EP3216040B1 - Conductive electrodes and their manufacturing process - Google Patents

Description

The invention relates to the field of electrochemical devices for storing electrical energy. It concerns in particular batteries and supercapacitors. It relates more particularly to electrodes comprising at least one metallic current collector coated with one or more protective layers formulated in aqueous base, the protective layer being placed between the current collector and the active material. The formulation of the aqueous-based protective layer has the advantage of avoiding the use of flammable, toxic organic solvents that are harmful to the environment. This system is used in aqueous electrolyte supercapacitors, the protective layer allowing a very significant reduction of the corrosion problems which are generally associated with the use of aqueous electrolytes. The protective layer makes it possible to improve the adhesion of the active material to the metal collector.

The electrodes of the invention can also be used as supercapacitor electrodes operating with an electrolyte of the ionic liquid type. In this case, the protective layer makes it possible to improve the adhesion and thus reduce the series equivalent resistance of the active material on the metal collector.

State of the prior art

Supercapacitors generally consist of the association of two conductive electrodes with a high specific surface, immersed in an ionic electrolyte and separated by an insulating membrane called a separator, which allows ionic conductivity and avoids electrical contact between the electrodes. Each electrode comprises at least one metallic current collector and one layer of active material. The metallic current collector allows the exchange of electrical current with an external system. Under the influence of a potential difference applied between the two electrodes, the ions present within an electrolyte are attracted by the surface having an opposite charge, thus forming a double electrochemical layer at the interface of each electrode. Electrical energy is thus stored electrostatically by charge separation.

• avec : E : la permittivité du milieu,
• S : la surface occupée par la double couche, et
• e : l'épaisseur de la double couche.

The expression of the capacitance of these supercapacitors is identical to that of conventional electrical capacitors, namely: C = ES/e

• with: E: the permittivity of the medium,
• S: the area occupied by the double layer, and
• e: the thickness of the double layer.

The achievable capacities within supercapacitors are much greater than those commonly reached by conventional capacitors, due to the use of porous electrodes with a high specific surface (maximization of the surface) and the extreme narrowness of the double electrochemical layer (a few nanometers).

The energy stored within the supercapacitor is defined according to the classic expression for capacitors, ie: E=1/2.CV ² , in which V is the electric potential of the supercapacitor.

Capacity and potential must therefore be high to optimize energy performance. The capacity depends on the porous texture actually accessible by the electrolyte.

The carbon electrodes used in super-capacitive systems must necessarily be: conductive, in order to ensure the transport of electric charges, porous, in order to ensure the transport of ionic charges and the formation of the double electric layer over a large surface , and chemically inert, to avoid any energy-consuming parasitic reactions.

The potential depends mainly on the nature of the electrolyte and in particular on the stability of the electrolyte under the influence of the electric field. There are different types of electrolytes. Organic electrolytes, that is to say comprising an organic salt dispersed in an organic solvent, make it possible to reach an operating potential of 2.7V. But these electrolytes are expensive, flammable, toxic and potentially polluting. They thus pose safety problems for use in a vehicle. Aqueous electrolytes are inexpensive and non-flammable, so they are more attractive for this application. In aqueous media, the applicable potential is 1.2V. Different aqueous electrolytes can be used, for example an aqueous solution of sulfuric acid, or potassium chloride, or potassium sulphate, or other salts in an acidic, basic or neutral medium.

The layer of active material being porous, and at least part of the electrode being immersed in the electrolyte, the current collector is likely to be corroded. by the aqueous electrolyte. Thus the lifetime of the electrode is reduced by the lack of corrosion resistance of the current collector.

Moreover, in the case where the collector is made of aluminium, in operation a passivation layer is formed composed of hydrated alumina Al ₂ O ₃ .xH ₂ O which protects it from corrosion. But this passivation layer, due to its ionic and electronic insulating properties, has the effect of increasing the resistance at the aluminum/active material interface.

Moreover, when the aluminum constitutes the positive current collector, this layer of alumina grows and densifies as the electrical cycles to which the supercapacitor is subjected. Aluminum can even, in contact with certain electrolytes, lose its passive character, which leads to its accelerated dissolution.

The same problems have been observed with other materials forming the current collectors, such as titanium.

To remedy all of these problems, various solutions have been proposed. Most consist of coating the current collector with one or more protective layers which are placed between the current collector and the active layer.

To allow satisfactory protection of the current collector, the protective layer must be impermeable to the electrolyte so as to prevent the latter from coming into contact with the metal collector and corroding it. It must be able to provide this protection over the entire operating temperature range of the system, typically up to 60°C. The protective layer must also ensure good electrical contact between the metal collector and the active material in order to have a minimum equivalent series resistance (ESR) of the supercapacitor. A low ESR is necessary for operation of the super-capacitor at high powers. It must exhibit satisfactory adhesion to the metallic material of which the current collector is made. Finally, the weight and the volume of the protective layer must be as low as possible in order to limit the mass and the volume of the super-capacitor. Since a preferred configuration for supercapacitor electrodes is a coiled configuration, another property of the electrodes must be their flexibility. Thus, the protective layer must also have flexibility properties.

Several layers of protection for the current collector have been described in the prior art:
To reduce corrosion and passivation problems, US 4,562,511 teaches to cover the aluminum collector with a paint loaded with conductive particles. However, this paint tends to increase the resistance of the system.

In EN 2824418 , a layer of paint comprising conductive particles, such as graphite or carbon black is applied between the collector and the active material, then is heated to eliminate the solvent. The paint is based on epoxy polymer and/or polyurethane. This paint is formulated in an organic solvent medium. This layer makes it possible to protect the collector in an organic medium. However, the behavior of such a collector in the presence of an aqueous electrolyte is not known.

US 2009/0155693 describes a method of forming a thin film of carbon on a current collector by depositing a dispersion of carbonaceous particles in an organic sol-gel type polymer matrix followed by the elimination of the sol-gel by thermal degradation at high temperature. This layer makes it possible to improve the conduction properties at the level of the contact. No information is given on watertightness in an aqueous medium. Moreover, the carbonaceous films obtained by this method are fragile and subject to abrasion during the assembly of the electrodes.

WO 200701201 and US2006/0292384 describe a protective layer for a metal collector, consisting of a polymer binder, which may be an epoxy, and carbonaceous conductive fillers in powder form. The experimental part describes a collector based on lead and a protective layer based on poly(vinyl chloride). This protective layer is impermeable to sulfuric acid. However, the collector protection compositions are formulated in an organic solvent medium. No information is given on the electrical contact between the metal collector and the active material. No information is given on sealing in other aqueous electrolytes, including 5M lithium nitrate in water.

FR2977364 describes metallic current collectors covered by a protective layer consisting of conductive fillers dispersed in a copolymer matrix. The system described improves the electrical contact between the metal commutator and the active material, as well as sealing against sulfuric acid. The copolymer used is based on vinyl chloride and/or vinyl acetate and the protective composition is prepared in an organic medium.

The document US2012/0237824 describes current collectors for lithium battery electrodes with corrosion resistance. The current collector is coated with a protective layer based on fluorinated resin. The protective layer may further contain as additives: fine rubber particles to improve flexibility, an adhesion promoter such as an epoxy resin, a crosslinking agent for the fluorinated resin in order to reduce its swelling. However, the protective compositions taught by this document are based on organic solvent.

JPH0582396 describes an assembly of a current collector made of a rubber-like material and a layer of active material, the assembly comprising an intermediate adhesive layer based on carbon black or graphite and a resin, which can be polycarbodiimide, ABS, epoxy, polyphenylene sulfate, urethane, acrylic, polyester resin. The adhesive composition is formulated in an organic solvent medium. The active layer is fixed on the current collector by hot pressing on the collector coated with the adhesive.

EP2207188 describes a supercapacitor electrode comprising a layer of active material formulated in an aqueous medium and comprising a conductive material, a binder of carboxymethylcellulose and of acrylic elastomer resin.

JP2000100441 describes an electrode for a lithium battery comprising a layer of active material comprising a conductive material, a binder based on a thermoplastic cross-linked elastomer, such as a polyester amide.

However, a layer of active material does not have the same characteristics as a protective layer of the current collector. In particular, the layer of active material must have a high porosity, unlike the protective layer.

EP 2 471 869 describes aqueous compositions based on polymers of the polysaccharide or polyamine type, a hydrophobic filler and a polyacid, these compositions being used to form a protective coating on an electrode.

JP 2014 199804 teaches a composition intended to promote adhesion between the current collector and the active electrode layer, this composition comprising a carbonaceous conductive material (A), a water-soluble resin (B) forming a binder, an aqueous dispersion of resin (C ) binding to fine particles.

There are currently no electrodes allowing the operation of a supercapacitor in an aqueous electrolyte, with a protective coating of the current collector formulated in aqueous base, the electrode exhibiting both low ESR, good corrosion resistance, high temperature stability over a large number of cycles, and satisfactory flexibility properties.

The invention has made it possible to solve these problems observed in the electrodes of the prior art.

Summary of the invention

1. (A) Une matrice de polymère comprenant :
   • (A1) Au moins un polymère ou un copolymère époxy réticulé,
   • (A2) Au moins un élastomère,
2. (B) Des charges conductrices,
   • caractérisée en ce que la couche de protection comprend :
     • de 30 à 60 % d'au moins un polymère ou un copolymère époxy réticulé (A1),
     • de 10 à 30 % d'au moins un élastomère (A2),
     • de 30 à 50 % de charges conductrices (B),
   • la somme des masses de (A1), (A2) et (B) représente de 95 à 100 %,
   • en masse de matière sèche, par rapport à la masse totale de matière sèche de la couche de protection (5).

The invention relates to an electrode for storing electrical energy comprising a metallic current collector and an active material, the current collector being coated on at least part of one of its faces by at least one protective layer. placed between the current collector and the active material, the protective layer comprising:

1. (A) A polymer matrix comprising:
   • (A1) At least one cross-linked epoxy polymer or copolymer,
   • (A2) At least one elastomer,
2. (B) Conductive fillers,
   • characterized in that the protective layer comprises:
     • from 30 to 60% of at least one crosslinked epoxy polymer or copolymer (A1),
     • from 10 to 30% of at least one elastomer (A2),
     • 30 to 50% conductive fillers (B),
   • the sum of the masses of (A1), (A2) and (B) represents 95 to 100%,
   • in mass of dry matter, relative to the total mass of dry matter of the protective layer (5).

1. 1- La fourniture d'un collecteur de courant métallique,
2. 2- La préparation d'une composition aqueuse (G),
3. 3- le dépôt de la composition (G) sur une partie au moins d'une face du collecteur de courant,
4. 4- un premier traitement thermique de séchage de la composition (G),
5. 5- un second traitement thermique du collecteur de courant revêtu à une température supérieure à la température de transition vitreuse du polymère ou du copolymère époxy réticulé (A1), et inférieure à la température de dégradation du polymère ou du copolymère époxy réticulé (A1),
6. 6- le dépôt d'une couche de matière active sur le collecteur de courant revêtu,

• ce procédé étant caractérisé en ce que la composition aqueuse (G) comprend :
  • de 30 à 60 % de précurseurs d'une matrice époxy réticulée (A1),
  • de 10 à 30 % d'au moins un élastomère (A2),
  • de 30 à 50 % de charges conductrices (B)
• et la somme des masses de (A1), (A2) et (B) représente de 95 à 100 %,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la composition aqueuse (G).

The invention also relates to a method of manufacturing an electrode comprising:

1. 1- The supply of a metallic current collector,
2. 2- The preparation of an aqueous composition (G),
3. 3- depositing composition (G) on at least part of one face of the current collector,
4. 4- a first heat treatment for drying the composition (G),
5. 5- a second heat treatment of the coated current collector at a temperature above the glass transition temperature of the polymer or crosslinked epoxy copolymer (A1), and below the degradation temperature of the crosslinked epoxy polymer or copolymer (A1),
6. 6- the deposition of a layer of active material on the coated current collector,

• this process being characterized in that the aqueous composition (G) comprises:
  • from 30 to 60% of precursors of a crosslinked epoxy matrix (A1),
  • from 10 to 30% of at least one elastomer (A2),
  • 30 to 50% conductive fillers (B)
• and the sum of the masses of (A1), (A2) and (B) represents from 95 to 100%,
• by mass of dry matter, relative to the total mass of dry matter of the aqueous composition (G).

The invention also relates to a supercapacitor comprising two electrodes of which at least a part is immersed in an ionic electrolyte, the two electrodes being separated by an insulating membrane, at least one of the two electrodes being according to the invention described below. above and illustrated in detail below.

• des précurseurs de la matrice de polymère (A) :
  • des précurseurs de polymère(s) ou de copolymère(s) époxy réticulé(s) (A1)
  • au moins un élastomère (A2),
• des charges conductrices (B).

According to a preferred embodiment, the protective layer is obtained by drying and crosslinking an aqueous composition (G) comprising:

• precursors of the polymer matrix (A):
  • precursors of crosslinked epoxy polymer(s) or copolymer(s) (A1)
  • at least one elastomer (A2),
• conductive fillers (B).

• des précurseurs de la matrice de polymère (A) :
  • des précurseurs de polymère(s) ou de copolymère(s) époxy réticulé(s) (A1)
  • au moins un élastomère (A2),
• des charges conductrices (B).

According to a preferred embodiment, the protective layer is obtained by drying and crosslinking an aqueous composition (G) consisting essentially of:

• precursors of the polymer matrix (A):
  • precursors of crosslinked epoxy polymer(s) or copolymer(s) (A1)
  • at least one elastomer (A2),
• conductive fillers (B).

According to a preferred embodiment, the current collector (3) is made of aluminum or copper.

According to a preferred embodiment, (A2) is chosen from: elastomers having a film forming temperature below 20°C.

According to a preferred embodiment, (A1) is chosen from: a crosslinked epoxy polymer, a crosslinked epoxy-alkyd copolymer, a mixture of epoxy polymer and crosslinked alkyd resin.

According to a preferred embodiment, (A1) is a crosslinked epoxy-alkyd copolymer.

According to a preferred embodiment, (A2) is chosen from butadiene-acrylonitrile (NBR) latexes and polyurethane latexes.

According to a preferred embodiment, (B) is chosen from: mixtures of carbon black and graphite.

• la composition de polymère (A) représente de 50 à 70 %,
• les charges conductrices (B) représentent de 30 à 50 %,

• et la somme des masses de (A) et de (B) représente de 95 à 100 %, avantageusement de 98 à 100%, et de manière préférée de 99 à 100%,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la couche de protection.

According to a preferred embodiment,

• the polymer composition (A) represents 50 to 70%,
• the conductive fillers (B) represent 30 to 50%,

• and the sum of the masses of (A) and (B) represents from 95 to 100%, advantageously from 98 to 100%, and more preferably from 99 to 100%,
• in mass of dry matter, relative to the total mass of dry matter of the protective layer.

• de 30 à 60 % d'au moins un polymère ou un copolymère époxy réticulé (A1),
• de 10 à 30 % d'au moins un élastomère (A2),
• de 30 à 50 % de charges conductrices (B),

• la somme des masses de (A1), (A2) et (B) représente de 98 à 100%, et de manière préférée de 99 à 100%,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la couche de protection.

According to a preferred embodiment, the protective layer comprises:

• from 30 to 60% of at least one crosslinked epoxy polymer or copolymer (A1),
• from 10 to 30% of at least one elastomer (A2),
• 30 to 50% conductive fillers (B),

• the sum of the masses of (A1), (A2) and (B) represents from 98 to 100%, and preferably from 99 to 100%,
• in mass of dry matter, relative to the total mass of dry matter of the protective layer.

According to a preferred embodiment, the protective layer has a thickness ranging from 5 to 50 μm.

According to a preferred embodiment, a primer layer is placed between the metallic current collector and the protective layer.

According to a preferred embodiment, a primer layer is placed between the protective layer and the active material.

According to a preferred embodiment, the method of the invention further comprises a step of preparing the current collector before the deposition of composition (G), this step comprising one or more steps chosen from: an abrasive treatment, a chemical.

According to a preferred embodiment of the process of the invention, the deposition of the composition (G) on the current collector is carried out using a film puller.

According to a preferred embodiment of the method of the invention, the deposition step 3- followed by drying 4- is implemented one or more times until a deposit thickness after drying of 5 to 50 μm is obtained. .

According to a preferred embodiment of the process of the invention, the treatment temperature in step 5- is from 120 to 160°C, preferably from 130 to 150°C.

1. (i) - préparation d'une composition aqueuse de matière active,
2. (ii) - dépôt de la composition de matière active sur la couche de protection,
3. (iii) - traitement thermique de séchage.

According to a preferred embodiment of the method of the invention, the preparation and deposition of the active ingredient comprises the following sub-steps:

1. (i) - preparation of an aqueous composition of active material,
2. (ii) - deposition of the composition of active material on the protective layer,
3. (iii) - drying heat treatment.

According to a preferred embodiment of the method of the invention, step 6- of depositing a layer of active material is carried out before step 5- of second heat treatment.

According to a preferred embodiment of the supercapacitor of the invention, the electrolyte is an aqueous electrolyte.

According to a preferred embodiment of the supercapacitor of the invention, the electrolyte is an ionic liquid.

According to a preferred embodiment of the supercapacitor of the invention, the two electrodes are according to the invention described above and illustrated in detail below.

detailed description The current collector :

In a known manner, the material used for the current collector can be, for example, aluminum and its alloys, copper and its alloys, stainless steel, nickel and its alloys, titanium and its alloys, and the materials resulting treatment of the surface of aluminum or stainless steel or titanium with carbon. Of these, aluminum and its alloys, copper and its alloys are preferred examples. Advantageously, the current collector is made of aluminum or copper. These materials can also be subjected to a surface oxidation treatment before use. The introduction of micro-reliefs on the surface of the current collector by a surface treatment is advantageous because it makes it possible to improve the adhesion of the material. The thickness of the current collector is generally in the range of 5 to 30 µm.

The protective layer:

The protective layer comprises a polymeric matrix (A) comprising at least at least one crosslinked epoxy polymer or copolymer (A1), and at least one elastomer (A2). It also comprises a charge-type conductive material (B).

• la matrice de polymère (A) représente de 50 à 70 %,
• les charges conductrices (B) représentent de 30 à 50 %,
• la somme des masses de (A) et de (B) représente de 95 à 100 %,

en masse de matière sèche, par rapport à la masse de matière sèche totale de la couche de protection.Preferably in the protective layer according to the invention:

• the polymer matrix (A) represents 50 to 70%,
• the conductive fillers (B) represent 30 to 50%,
• the sum of the masses of (A) and (B) represents 95 to 100%,

by mass of dry matter, relative to the total dry matter mass of the protective layer.

Preferably the sum of the masses of (A) and (B) represents from 98 to 100%, even more preferably from 99 to 100%, by mass of dry matter, relative to the total mass of dry matter of the layer of protection.

By polymer matrix is meant within the meaning of the present invention a material resulting from the drying and optionally from the crosslinking of polymers, copolymers, crosslinking agents, and additives, such as in particular crosslinking catalysts, surfactants, dispersing agents, wetting agents.

The polymer matrix is obtained from a polymer composition, by drying and crosslinking. In practice, the polymer composition is mixed with the other components, in particular the electrically conductive fillers, to form a coating composition or protective composition (G) in the form of an aqueous dispersion. The protective composition is dried and then subjected to a treatment (heating for example) which triggers the crosslinking reaction. The polymer matrix forms as a result of this treatment. The protective layer is then obtained.

• de 30 à 60 % d'une matrice époxy réticulée (A1),
• de 10 à 30 % d'au moins un élastomère (A2),
• de 30 à 50 % de charges conductrices (B)

• et la somme des masses de (A1), (A2) et (B) représente de 95 à 100 %,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la couche de protection.

According to the invention, the protective layer comprises:

• from 30 to 60% of a crosslinked epoxy matrix (A1),
• from 10 to 30% of at least one elastomer (A2),
• 30 to 50% conductive fillers (B)

• and the sum of the masses of (A1), (A2) and (B) represents from 95 to 100%,
• in mass of dry matter, relative to the total mass of dry matter of the protective layer.

Preferably the sum of the masses of (A1), (A2) and (B) represents from 98 to 100%, even more preferably from 99 to 100%, by mass of dry matter, relative to the total mass of dry matter of the protective layer.

The polymer matrix (A):

• (A1) Au moins un polymère ou un copolymère époxy réticulé,
• (A2) Au moins un élastomère.

The polymer matrix (A) comprises:

• (A1) At least one cross-linked epoxy polymer or copolymer,
• (A2) At least one elastomer.

By polymer matrix is preferably meant within the meaning of the present invention a material consisting essentially of polymers, copolymers, crosslinking agents, and additives used for the manufacture of this matrix, such as in particular crosslinking catalysts, surfactants.

Preferably, the polymer matrix (A) essentially consists of one or more crosslinked epoxy polymer(s) or copolymer(s), one or more elastomers, crosslinking agents, crosslinking catalysts, surfactants, dispersing agents, wetting agents.

Preferably, (A1) is chosen from: a crosslinked epoxy polymer, a crosslinked epoxy-alkyd copolymer, a mixture of epoxy polymer and crosslinked alkyd resin.

Even more preferably (A1) is a crosslinked epoxy-alkyd copolymer.

• les résines époxy glycidyle qui sont préparées par une réaction de condensation du composé dihydroxy approprié avec un diacide ou une diamine et avec de l'épichlorhydrine, comme par exemple le diglycidyl éther de bisphénol A (DGEBA)
• les résines époxy Novolac qui sont des glycidyléthers de résines phénoliques Novolac. Elles sont obtenues par réaction du phénol avec le formaldéhyde en présence d'un catalyseur acide pour produire une résine phénolique Novolac, suivie d'une réaction avec l'épichlorhydrine.

As an example of epoxy resin, we can cite:

• glycidyl epoxy resins which are prepared by a condensation reaction of the appropriate dihydroxy compound with a diacid or a diamine and with epichlorohydrin, such as for example diglycidyl ether of bisphenol A (DGEBA)
• Novolac epoxy resins which are glycidyl ethers of Novolac phenolic resins. They are obtained by reaction of phenol with formaldehyde in the presence of an acid catalyst to produce a phenolic resin Novolac, followed by a reaction with epichlorohydrin.

As an example of an epoxy-alkyd copolymer, mention may be made of an alkyd resin containing a carboxyl group with which the epoxy resin has been reacted by a carboxy/epoxy esterification reaction.

Among the crosslinking agents, mention may be made of amine crosslinkers such as melamines, in particular hexamethoxymethylmelamine.

Preferably, the crosslinking agent represents from 10 to 40%, preferably from 15 to 35%, even better from 20 to 30%, by mass relative to the mass of (A1) in dry matter.

Preferably, the catalyst is used in an amount ranging from 0.1 to 2.5% by mass relative to the mass of crosslinking agent, in dry matter.

Among the catalysts, mention may be made of paratoluene sulphonic acid.

Preferably (A1) is a crosslinked epoxy matrix, that is to say a material resulting from the crosslinking of an epoxy polymer composition. Preferably (A1) is a material obtained from a polymer composition of which at least 30% by mass of dry matter consists of epoxy polymer or epoxy fragments in a copolymer. Preferably (A1) is a material consisting essentially of a crosslinked epoxy polymer or a crosslinked epoxy copolymer or a crosslinked mixture of an epoxy and another polymer, such as an alkyd resin. It can remain in (A1) more or less significant quantities of uncrosslinked polymer or copolymer, of unreacted crosslinking agent, the catalyst, the surfactants, the wetting agents, the dispersants.

(A1) is implemented in the invention in the form of a polymer composition (C _A1 ). It is an aqueous composition which comprises the (co)polymer or the mixture of (co)polymers, the crosslinking agent, the catalyst and optionally surfactants. Such compositions are commercially available or can be easily prepared from commercially available products.

Preferably the elastomer (A2) is an elastomer or a mixture of elastomers chosen from elastomers having a film forming temperature below 20°C.

(A2) can be chosen from crosslinked or non-crosslinked elastomers, it can be chosen from natural or synthetic latexes such as butadiene-acrylonitrile (NBR) latexes, hydrogenated butadiene-acrylonitrile (NBR) latexes, polyurethane latexes , acrylic latexes, styrene butadiene (SBR) latexes, butyl latexes, acrylonitrile-butadiene-styrene (ABS) latexes, and mixtures thereof.

(A2) can be crosslinked simultaneously with the crosslinking of (A1), under the effect of the same crosslinking agent as (A1) or under the action of a specific crosslinking agent.

Preferably (A2) is chosen from butadiene-acrylonitrile (NBR) latexes and polyurethane latexes.

(A2) is implemented in the invention in the form of a latex composition (C _A2 ). It is an aqueous composition which comprises the elastomer and surfactants. It may also comprise crosslinking agents. Such compositions are commercially available or can be easily prepared from commercially available products.

• de 30 à 60 % d'une matrice (A1) choisie parmi : un polymère époxy réticulé, un copolymère époxy-alkyde réticulé, un mélange de polymère époxy et de résine alkyde réticulé,
• de 10 à 30 % d'au moins un élastomère (A2) choisi parmi : les latex butadiène-acrylonitrile (NBR) et les latex polyuréthanes,
• de 30 à 50 % de charges conductrices (B)

• et la somme des masses de (A1), (A2) et (B) représente de 95 à 100 %, avantageusement 98 à 100%, encore plus préférentiellement de 99 à 100%,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la couche de protection.

According to a preferred embodiment, the protective layer comprises:

• from 30 to 60% of a matrix (A1) chosen from: a crosslinked epoxy polymer, a crosslinked epoxy-alkyd copolymer, a mixture of epoxy polymer and crosslinked alkyd resin,
• from 10 to 30% of at least one elastomer (A2) chosen from: butadiene-acrylonitrile (NBR) latexes and polyurethane latexes,
• 30 to 50% conductive fillers (B)

• and the sum of the masses of (A1), (A2) and (B) represents from 95 to 100%, advantageously 98 to 100%, even more preferably from 99 to 100%,
• in mass of dry matter, relative to the total mass of dry matter of the protective layer.

Composition (G):

• des précurseurs de la matrice de polymère (A) :
  • des précurseurs de polymère(s) ou de copolymère(s) époxy réticulé(s) (A1)
  • au moins un élastomère (A2),
• des charges conductrices (B).

According to the invention, the protective layer is obtained by drying and crosslinking an aqueous composition (G) comprising:

• precursors of the polymer matrix (A):
  • precursors of crosslinked epoxy polymer(s) or copolymer(s) (A1)
  • at least one elastomer (A2),
• conductive fillers (B).

• les précurseurs de la matrice de polymère (A) représentent de 50 à 70%,
• les charges conductrices (B) représentent de 30 à 50 %,

• la somme des masses de (A) et de (B) représente de 95 à 100 %,
• en masse de matière sèche, par rapport à la masse de matière sèche totale de la composition aqueuse (G).

Preferably, in the aqueous composition (G):

• the precursors of the polymer matrix (A) represent 50 to 70%,
• the conductive fillers (B) represent 30 to 50%,

• the sum of the masses of (A) and (B) represents 95 to 100%,
• by mass of dry matter, relative to the mass of total dry matter of the aqueous composition (G).

Preferably, the sum of the masses of (A) and (B) represents from 98 to 100%, even better from 99 to 100% by mass of dry matter, relative to the mass of total dry matter of the aqueous composition ( G).

• de 30 à 60 % de précurseurs d'une matrice époxy réticulée (A1),
• de 10 à 30 % d'au moins un élastomère (A2),
• de 30 à 50 % de charges conductrices (B)

• et la somme des masses de (A1), (A2) et (B) représente de 95 à 100 %,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la composition aqueuse (G).

According to the invention, the aqueous composition (G) comprises:

• from 30 to 60% of precursors of a crosslinked epoxy matrix (A1),
• from 10 to 30% of at least one elastomer (A2),
• 30 to 50% conductive fillers (B)

• and the sum of the masses of (A1), (A2) and (B) represents from 95 to 100%,
• by mass of dry matter, relative to the total mass of dry matter of the aqueous composition (G).

Preferably, the sum of the masses of (A1), (A2) and (B) represents from 98 to 100%, even better from 99 to 100% by mass of dry matter, relative to the mass of total dry matter of the aqueous composition (G).

• de 30 à 60 % de précurseurs d'une matrice époxy réticulée (A1), (A1) étant choisie parmi : un polymère époxy réticulé, un copolymère époxy-alkyde réticulé, un mélange de polymère époxy et de résine alkyde réticulé,
• de 10 à 30 % d'au moins un élastomère (A2) choisi parmi : les latex butadiène-acrylonitrile (NBR) et les latex polyuréthanes,
• de 30 à 50 % de charges conductrices (B)

• et la somme des masses de (A1), (A2) et (B) représente de 95 à 100 %, avantageusement 98 à 100%, encore plus préférentiellement de 99 à 100%,
• en masse de matière sèche, par rapport à la masse totale de matière sèche de la composition aqueuse (G).

According to a preferred embodiment, the aqueous composition (G) comprises:

• from 30 to 60% of precursors of a crosslinked epoxy matrix (A1), (A1) being chosen from: a crosslinked epoxy polymer, a crosslinked epoxy-alkyd copolymer, a mixture of epoxy polymer and crosslinked alkyd resin,
• from 10 to 30% of at least one elastomer (A2) chosen from: butadiene-acrylonitrile (NBR) latexes and polyurethane latexes,
• 30 to 50% conductive fillers (B)

• and the sum of the masses of (A1), (A2) and (B) represents from 95 to 100%, advantageously 98 to 100%, even more preferably from 99 to 100%,
• by mass of dry matter, relative to the total mass of dry matter of the aqueous composition (G).

By precursors of the polymer matrix, we mean the monomers, pre-polymers, polymers and copolymers, the crosslinking agents and the additives used for the manufacture of this matrix, such as in particular crosslinking catalysts, surfactants, dispersing agents, wetting agents.

The proportion of the components of the protective layer is controlled by the choice of the proportions of the components of the protective composition (G).

In known manner, the heat treatment is carried out at a temperature and for a duration sufficient to bring about the crosslinking of the epoxy polymer(s) or copolymer(s).

The aqueous composition (G) can be prepared by mixing the various constituents of (C _A1 ), (C _A2 ) and (B) in any order: for example the conductive fillers can be introduced in part into (C _A1 ) and (C _A2 ) before the mixing of the latter or they can be introduced after (C _A1 ) and (C _A2 ) have been mixed.

To facilitate obtaining a stable and homogeneous composition, surfactants, dispersing agents, wetting agents and water-miscible solvents such as alcohols, in particular ethanol or isopropanol.

The aqueous composition (G) has a dry extract which is advantageously from 25 to 50%, preferably from 30 to 45% by mass. The choice of the dry extract is adapted by those skilled in the art according to the method of application of the composition.

Conductive load:

By electrically conductive filler within the meaning of the invention is meant a filler having a volume resistivity of 1×10 ^-9 at 1 Ω.cm. The preferred volume resistivity is 1 × 10 ^-6 to 1 × 10 ^-1 Ω.cm.

The electrically conductive filler can be chosen for example from electrically conductive carbon fillers.

These electrically conductive fillers can be in the form of particles, in the form of fibers, or a mixture of different types of fillers.

Among the carbon fillers in the form of particles, mention may be made of carbon black, acetylene black, nanoporous carbon, graphite (natural graphite, artificial graphite). An average primary particle diameter of 0.002 to 20 μm and in particular of 0.025 to 10 μm is preferred for obtaining high electrical conductivity.

Among the carbon fillers in the form of fibers, mention may be made of carbon fibers, carbon nanotubes, carbon nanofibers.

The conductive filler preferably consists of at least one filler selected from the group consisting of carbon black, acetylene black, nanoporous carbon, graphite, carbon fibers, carbon nanotubes, and nanofibers of carbon. Preferably, the invention is implemented with a filler chosen from: mixtures of carbon black and graphite. Advantageously, mixtures having a mass proportion of carbon black/graphite ranging from 4/1 to 1/1 are chosen as conductive filler.

The electrically conductive filler is preferably incorporated in quantities ranging from 30 to 50% by mass of dry matter relative to the mass of dry matter of the protective composition or of the aqueous composition (G).

It is preferable to implement at least 30% by mass of electrically conductive fillers to obtain satisfactory electrical conductivity of the protective layer. On the other hand, the manufacture of the composition is problematic when more than 50% by weight of electrically conductive fillers are used: ease of mixing, stability of the coating on deposition and during drying.

Surfactants:

Advantageously, the aqueous composition (G) comprises at least one surfactant. Surfactants can be implemented to fulfill several functions in the electrically conductive protective layer. They can be introduced into (C _A1 ), into (C _A2 ) and/or after mixing (C _A1 ), (C _A2 ) and (B).

Their role lies mainly in the formulation of the composition in the wet state, before and during application to the current collector, in order, without limitation: to improve the ability to disperse the conductive charge of the electricity, improve the stability of polymers and copolymers in the composition, improve the spreading properties of the coating. Some surfactants evaporate during the heat treatment, others remain in the protective composition.

Other components:

Electrically non-conductive fillers can also be used in the protective composition in addition to the electrically conductive filler. Examples of electrically non-conductive filler are: electrically non-conductive carbon; inorganic oxides; resins. The nature and the quantity of fillers are chosen according to the implementation properties (rheology) and the usage properties (adhesion properties, electrical resistance) of the electroconductive protective layer.

It is also possible to implement in the protective composition, and in a non-limiting manner: an adhesion promoter in order to improve the adhesion between the current collector and the electrically conductive layer.

Among the adhesion promoters, mention may be made, for example, of an acrylic polymer or an acrylic olefin copolymer.

These components can be introduced into (C _A1 ), into (C _A2 ), be mixed with the conductive fillers (B) and/or be introduced after the mixing of (C _A1 ), (C _A2 ) and (B).

Preferably, the other components represent at most 5% by mass of the total mass of the coating layer and of the aqueous composition (G), in dry matter. Advantageously, they represent at most 2% and even better still 1% by mass of the total mass of the coating layer and of the aqueous composition (G), in dry matter.

Additional layers:

The protection layer is placed between the current collector and the active material. Provision can also be made for a primer layer to be placed between the metallic current collector and the protective layer, the primer layer comprising a water-dispersible binder and conductive fillers. For example, the water-dispersible binder can be a polyurethane latex.

• de 60 à 70 % d'au moins un liant hydrodispersable,
• de 30 à 40% de charges conductrices, en masse par rapport à la masse totale de la couche d'apprêt, en matière sèche, le liant hydrodispersable et les charges conductrices représentant de 95 à 100% de la matière sèche de la couche d'apprêt.

The primer coat may include:

• from 60 to 70% of at least one water-dispersible binder,
• from 30 to 40% of conductive fillers, by mass relative to the total mass of the primer layer, in dry matter, the water-dispersible binder and the conductive fillers representing from 95 to 100% of the dry matter of the layer of primer.

According to another variant, a primer layer can be placed between the protective layer and the active layer. This variant is particularly advantageous for ionic liquid cells, for which it increases the lifetime. Preferably this layer is between 5 and 20 micrometers thick.

• Une étape de préparation d'une composition comportant 60% à 70% de liant hydrodispersable, et 30% à 40% de charges conductrices, en complément afin d'atteindre un total de 95 à 100% en poids en matière sèche, diluée dans un solvant aqueux ;
• Une étape de dépôt de la dite composition sur la couche de protection ;
• Une étape de séchage du collecteur de courant métallique.

For example, one proceeds according to the following steps, after the formation of the protective layer and the formation of the active layer:

• A step of preparing a composition comprising 60% to 70% of water-dispersible binder, and 30% to 40% of conductive fillers, in addition in order to reach a total of 95 to 100% by weight in dry matter, diluted in a aqueous solvent;
• A step of depositing said composition on the protective layer;
• A step of drying the metallic current collector.

The operation of depositing and drying a layer of primer can be repeated as many times as necessary to obtain the desired thickness.

Electrode manufacturing process:

1. 1- La fourniture d'un collecteur de courant métallique,
2. 2- La préparation d'une composition aqueuse (G) comprenant :
   • Au moins un polymère ou un copolymère époxy et au moins un agent réticulant,
   • Au moins un élastomère,
   • Des charges conductrices,
3. 3- le dépôt de la composition (G) sur une partie au moins d'une face du collecteur de courant,
4. 4- un premier traitement thermique du collecteur de courant revêtu de (G) à une température allant de 25 à 60°C,
5. 5- un second traitement thermique du collecteur de courant revêtu de la composition (G) séchée, à une température supérieure à la température de transition vitreuse du polymère ou du copolymère époxy réticulé, et inférieure à la température de dégradation du polymère ou du copolymère époxy réticulé,
6. 6- le dépôt d'une couche de matière active sur le collecteur de courant revêtu de la couche de protection ou de la composition (G) simplement séchée.

Another subject of the invention is a process for manufacturing an electrode comprising:

1. 1- The supply of a metallic current collector,
2. 2- The preparation of an aqueous composition (G) comprising:
   • At least one epoxy polymer or copolymer and at least one crosslinking agent,
   • At least one elastomer,
   • conductive fillers,
3. 3- depositing composition (G) on at least part of one face of the current collector,
4. 4- a first heat treatment of the current collector coated with (G) at a temperature ranging from 25 to 60°C,
5. 5- a second heat treatment of the current collector coated with the dried composition (G), at a temperature above the glass transition temperature of the crosslinked epoxy polymer or copolymer, and below the degradation temperature of the epoxy polymer or copolymer reticle,
6. 6- the deposition of a layer of active material on the current collector coated with the protective layer or with the composition (G) simply dried.

The aqueous composition (G) used in the process is that which has been described above, the preferred variants of the process corresponding to the preferred variants for the choice of the components of (G).

The method of the invention may comprise, before the deposition of the aqueous composition (G), a preparation of the current collector, this step comprising one or more steps chosen from: an abrasive treatment (silicon carbide paper for example), an etching chemical (e.g. acetone wash, wash with a mixture of hydrofluoric acid and nitric acid).

In a known manner, the deposition of the composition (G) on the current collector can be carried out using a film puller, or by any other method known to those skilled in the art, such as application with a brush. , rolling...

The deposition can be carried out on the whole of one face of the current collector or on only one part. The deposit is made at least on the part of the current collector which will be immersed in the electrolyte.

After this deposition, the composition is dried by applying a heat treatment at a temperature of preferably 25 to 60°C, even better still 30 to 50°C. The treatment is applied for a period of 15 minutes to 1 hour, preferably about 30 minutes. This step can for example be implemented in an oven so as to benefit from a controlled atmosphere.

The deposition step 3- followed by drying 4- can be implemented once or it can be repeated so as to increase the thickness of the deposit.

Preferably, the deposition step(s) are carried out so as to obtain a deposition thickness after drying of 5 to 50 μm.

Once a deposit of the desired thickness has been obtained, a second heat treatment is carried out at a temperature above the glass transition temperature of the epoxy polymer or copolymer, and below the degradation temperature of the polymer or epoxy copolymer. of the epoxy copolymer, so as to form a polymer network by reacting the crosslinking agent with the polymer(s) or the copolymer(s).

Advantageously, the treatment temperature in step 5- is from 120 to 160°C, preferably from 130 to 150°C.

The active material which is implemented can be chosen from the materials known from the prior art for this use, in particular those described in the application EN 2985598 .

1. (i) - préparation d'une composition aqueuse de matière active par exemple à partir de noir de carbone, d'alcool polyvinylique, d'acide poly(acrylique) et de carboxyméthylcellulose,
2. (ii) - dépôt de la composition de matière active sur la couche de protection par exemple à l'aide d'un tire-film,
3. (iii) - traitement thermique de séchage, par exemple pendant 30 minutes à 50°C,
4. (iv) - traitement thermique de réticulation, par exemple pendant 30 minutes à 140°C.

In cases where the active ingredient is derived from an aqueous carbon composition, the deposition and drying of the active ingredient may include the following sub-steps:

1. (i) - preparation of an aqueous composition of active material, for example from carbon black, polyvinyl alcohol, poly(acrylic) acid and carboxymethylcellulose,
2. (ii) - deposition of the composition of active material on the protective layer, for example using a film puller,
3. (iii) - drying heat treatment, for example for 30 minutes at 50° C.,
4. (iv) - crosslinking heat treatment, for example for 30 minutes at 140°C.

Provision can be made for step 6- of depositing a layer of active material to be carried out before step 5- of second heat treatment. After the implementation of steps 1- to 4-, steps (i) to (iii) are carried out and then step 5- of the second heat treatment is applied, which makes it possible to simultaneously crosslink the protective layer and the active layer.

The method of the invention may optionally comprise, between steps 1- and 2-, the deposition of a layer of primer, as described above, on the current collector, followed by the drying of the layer of 'primer.

Such electrodes have advantageous properties when they are implemented in a supercapacitor. In a capacitor operating with an electrolyte of the ionic liquid type, the function of the protective layer is to improve the adhesion and to reduce the equivalent series resistance of the active material on the metal collector.

In a capacitor operating with an aqueous electrolyte, the protective layer has the function of protecting the current collector against corrosion, improving adhesion and reducing the equivalent resistance in series of the active material on the metallic collector. Thus, it helps to increase the life of the capacitor.

Figures:

• Figure 1 : schematic representation of the structure of a supercapacitor
• Figure 2 : schematic representation of the assembly implemented to carry out the transverse resistance measurement (ESR test)
• Figure 3 : schematic representation of a sample for the dynamic corrosion test
• Figure 4 : schematic representation of a dynamic corrosion test setup

In the figures, the same reference is used to designate the same element in different diagrams.

The figure 1 is a schematic representation of the structure of a supercapacitor 1. The supercapacitor 1 comprises two conductive electrodes 2 immersed in an ionic electrolyte (not shown) and separated by an insulating membrane called separator 9, which allows ionic conductivity and avoids electrical contact between the electrodes 2.

Each electrode 2 comprises a metallic current collector 3, for example copper or aluminum, covered with a conductive protective layer 5, for example with a thickness of between 5 and 50 micrometers, as well as a monolithic active material 7, for example in carbon, in contact with the separator 9.

The protective layer 5 improves the contact between the current collector and the active layer 7, it protects the metallic current collector 3 against the reactive species present in the electrolyte.

The protective layer 5 is impermeable to aqueous electrolytes, in particular in an acid medium, for example at a pH less than or equal to 4, or even in a neutral medium at a pH of 7. This sealing thus allows protection of the metallic current collector 3 against corrosion in aqueous media, thus preventing deterioration of the electrical contact between said metallic current collector 3 and the monolithic active material 7.

In addition, the conductive protective layer 5 also allows an improvement in the electrical contact between said metallic current collector 3 and the monolithic active material 7.

According to a first embodiment, an electrochemical energy storage device is formed by superimposing a plurality of multilayer unit assemblies conforming to the one shown on the figure 1 . This first embodiment typically corresponds to a supercapacitor structure.

The device can be obtained by rolling up the multilayer unitary assembly or by stacking a plurality of multilayer unitary assemblies. The assembly thus presents a repetitive pattern defined by the unitary assembly represented on the figure 1 .

Experimental part : I- Materials and methods : I - 1. Materials:

• Binder (A1): it is obtained from RESYDROL AX 906W ^® resin (CYTEC) by crosslinking. It is a resin dispersed at 35% in aqueous phase, containing epoxy and alkyd functions. It is cross-linked with a hexamethoxymethylmelamine to form a thermosetting polymer. The cross-linking agent used is CYMEL ^® 303 (CYTEC). This reaction is catalyzed by a para-toluene sulphonic acid, CYCAT 4040 ^® (CYTEC) previously dispersed in ethanol.
• Binder (A2):
  • LITEX NX 1200 ^® (SYNTHOMER): butadiene-acrylonitrile latex dispersed at 45% in aqueous phase
    Where
  • PU6800 (ALBERDINGK): polyurethane latex dispersed in aqueous phase at 33%.
• Fillers: The conductive fillers (B) used are carbon black (ENSACO 260G ^® ) and graphite (TIMCAL, Timrex KS6L ^® ).
• Additives: A silicone surfactant is added to the formulation in order to reduce the surface tension and thus improve the wettability of the coating on the substrate. This agent is BYK ^® 349.
• Metal strips: 20µm thick aluminum foil

In the experimental part, unless otherwise indicated, all the ratios are given by mass.

I - 2. Methods of manufacturing articles : - Coating of the protective coating:

55 microns of the protective composition are deposited on the first side of a metal strip using a film puller via an Elcometer ^® allowing a homogeneous and controlled deposit. After 30 minutes of drying at 50°C, the strips covered are then treated at 140° C. for 30 minutes. The coating thickness is measured using a micrometer, and is between 15 to 20 microns. A second layer is produced in the same way in order to obtain a total thickness of approximately 35 μm.

- Manufacture of cells:

The coating of the coating is the same as described above.

Variant 1 (electrodes of tables 7 to 12): Subsequently, the coated strips intended for the first electrode are coated with 305 μm of active material prepared according to example 1 of the application EN 2985598 , so that an active layer thickness of 150 μm is obtained after drying for 30 min at 50°C. All the layers are cured simultaneously for 30 min at 140°C.

The same process is carried out to manufacture the second electrode, with a dry thickness of active material of 90 μm, ie 155 μm wet.

Variant 2 (electrodes from table 13):

55 μm of a primer layer defined in table A (formulation 4) are deposited on the coating layer. The metallic current collector is subjected to drying for a period of 30 min at a temperature of 50° C. so as to obtain a layer with a thickness of 20 ± 3 micrometers. The same amount is deposited on both electrodes.

The coated strips intended for the first electrode are coated with 410 μm of active material according to example 1 of the application EN 2985598 , so that an active layer thickness of 200 μm is obtained after drying for 30 min at 50°C. All of the layers are cured simultaneously for 30 minutes at 140°C.

The same process is carried out for the second electrode, with a dry mass of double-sided active material of 150 μm, ie 305 μm wet.

The model cells are obtained by assembling two electrodes between which a cellulose separator is placed.

Aqueous electrolyte cell: the assembly is filled with 5M lithium nitrate electrolyte in water and protected between two 90µm heat-sealable plastic films.

Ionic liquid cell: the assembly is filled, under a controlled atmosphere, with 98% EMIM BF4 (1-ethyl 3-methylimidazolium tetrafluoroborate), protected between two 90 µm heat-sealable plastic films.

I - 3. Test and characterization methods:

Coated strips are characterized using four different test methods:
Test 1: A transverse resistance test (in mΩ) is carried out by pressurizing (200N), a 3 cm ² square 11 of two collector strips 3 coated with a protective layer 5 ( picture 2 ).

This measurement makes it possible to apprehend the compatibility at the interface of the different layers. The measured resistance should be as low as possible to allow high power operation of the supercapacitor.

To evaluate the resistance of the system, Ohm's law U=RI is used.

The intensity of the current is fixed at 1 ampere and a potential sweep is carried out. A straight line I=f(U) is then obtained. Resistance can be calculated. The software used to process the data is EC-Lab ^® software.

The specifications are as follows: Collector + coating transverse resistance < 50 mΩ

Test 2: A winding test around a mandrel makes it possible to examine the ability to stretch and adhere to a collector coated with a protective layer. Any damage such as cracks and/or scales is detected visually.

The coating is applied to the metal collector, under the same conditions as described above. During the test, the sample is uniformly bent for 1 to 2 seconds through 180° around the mandrel. The bending is started with the largest bending diameter and the test is continued up to the diameter for which the coating shows cracks. In the tests implemented within the framework of the invention, this test must be validated for a mandrel of 3 mm in diameter. The PF 5710 ^® reference chucks come from the company BYK.

The specifications are as follows: Winding without cracks around a mandrel of 3mm in diameter

Test 3: Dynamic corrosion measurement at room temperature

This measurement is based on a 3-electrode assembly at 0.8V.

• une électrode de référence au calomel saturée 15,
• une électrode de travail 2 (représentée de façon détaillée sur la figure 3) constituée du collecteur 3 recouvert du revêtement de protection sur une partie de sa surface 3.1 et non revêtu sur la partie 3.2 qui n'est pas immergée dans l'électrolyte, un revêtement par un film plastique 13 protège le verso (non représenté) et les bords du collecteur 3
• une contre électrode 17 en acier inoxydable. Les trois électrodes sont plongées dans un bécher rempli d'électrolyte 19 de 180mL.

The three electrodes used are ( figure 4 ):

• a saturated calomel reference electrode 15,
• a working electrode 2 (shown in detail on the picture 3 ) consisting of the collector 3 covered with the protective coating on part of its surface 3.1 and not coated on the part 3.2 which is not immersed in the electrolyte, a coating by a plastic film 13 protects the back (not shown) and collector edges 3
• a counter electrode 17 made of stainless steel. The three electrodes are immersed in a beaker filled with electrolyte 19 of 180 mL.

A current is then sent through the electrodes. In the context of the present invention, the current sent is 0.8 V because the solution is an aqueous solution.

The purpose of this test is to evaluate the variation of the intensity of the current as a function of time. If I is constant, there is no corrosion, if I is not constant, a corrosion phenomenon is present.

If the protective conductive coating lasts 23 hours then the test is validated.

The objective of this measurement is to force the oxidation and therefore the passivation of the aluminum in order to evaluate the performance of the system under conditions as close as possible to real cases. This test is performed only if all the other tests pass.

Test 3+: dynamic corrosion measurement at 60°C

For certain applications, in particular in the automobile when the supercapacitor must be placed near a hot spot, a high resistance in temperature, up to 60°C can be necessary. This is why a dynamic corrosion test at 60°C has also been carried out in some cases. This test is optional at this time. Its implementation is identical except for the assembly temperature which is raised to 60°C for the duration of the test. If the protective conductive coating lasts 40 hours then the test is validated.

Test 4: measurement of the performance of an electrode in the aqueous electrolyte cell

Starting from a cell comprising the electrodes according to the invention, cycling is carried out at room temperature and cycling at 60° C. Charge-discharge cycles from 0 to 1.5V are implemented. An initial and final ESR test of the complete system is carried out after 90,000 cycles for the test at room temperature and after 10,000 cycles for the test at 60°C.

• ESR final < 2 x ESR initial pour un cyclage à température ambiante > 90 000 cycles
• ESR final < 2 x ESR initial pour un cyclage à 60°C > 10 000 cycles.

The specifications are:

• Final ESR < 2 x initial ESR for cycling at room temperature > 90,000 cycles
• Final ESR < 2 x initial ESR for cycling at 60°C > 10,000 cycles.

Test 5: measurement of the performance of an electrode in the ion electrolyte cell

The test proceeds like test 4 above, with charge-discharge cycles from 0 to 3V. The evaluation of the overall performance of the system (collector + protective coating + active material) is carried out within closed cells.

• Voltage (V) > 3
• Capacité (F) > 10
• ESR (mΩ) < 70

The specifications are as follows:

• Voltage (V) > 3
• Capacity (F) > 10
• ESR (mΩ) < 70

Test 6: calendar measurement of the performance of an electrode in the ion electrolyte cell

From a cell comprising the electrodes according to the invention, a DC voltage (3V) is applied at ambient temperature. The evaluation of the overall performance of the system (collector + coatings + active material) is carried out within closed cells.

• Voltage (V) > 3
• Capacité (F) > 10
• ESR (mΩ) < 70

The specifications are as follows:

• Voltage (V) > 3
• Capacity (F) > 10
• ESR (mΩ) < 70

The test is stopped when the cell becomes shorted.

II - Production of coatings for the manufacture of a super-capacitor operating with an aqueous electrolyte:

Illustrated below are examples of formulations for the manufacture of a protective conductive layer intended to coat a metallic current collector.

II - 1. Wordings - Formulation 1 (F1.1 and F1.2): epoxy resin dispersed in aqueous phase

Different compositions described in Table 1 are mixed to give a paste. The formulation is expressed at 100% before addition of the catalyst in dispersion in ethanol.

The solvent is water. The dry extract of the complete formulation (including ethanol) is 40%. Table 1: Composition of formulation 1 Wording 1: F1.1 F1.2 RESYDROL AX906W 35% in water 42.45 43.18 BYK 349 0.30 0.31 WATER 31.40 31.94 TIMREX KS6L 6.73 6.85 ENSACO 260G 13.46 13.69 CYMEL 303 98% in water 5.66 4.03 Total wet 100.00 100.00 CYCAT 4040 40% in isopropanol 0.075 0.075 ETHANOL 10.00 10.00

The catalyst/crosslinker percentage was then varied from formulation F1.1 Table 2: Variants of formulation 1 with variation of the percentage of catalyst in formula F1.1 Formulation 1 F1.3 F1.4 F1.1 F1.5 F1.6 F1.7 RESYDROL AX906W 35% in water 42.45 42.45 42.45 42.45 42.45 42.45 BYK 349 0.30 0.30 0.30 0.30 0.30 0.30 WATER 31.40 31.40 31.40 31.40 31.40 31.40 TIMREX KS6L 6.73 6.73 6.73 6.73 6.73 6.73 ENSACO 260G 13.46 13.46 13.46 13.46 13.46 13.46 CYMEL 303 98% in water 5.66 5.66 5.66 5.66 5.66 5.66 Total wet 100.00 100.00 100.00 100.00 100.00 100.00 CYCAT 4040 0.019 0.034 0.075 0.150 0.226 0.301 ETHANOL 10.00 10.00 10.00 10.00 10.00 10.00

Formulation 2: choice and formulation of a latex that will be added to the formulation1

To improve the performance of the epoxy resin-based formulation, a latex formulation chosen from those described in Table 3 is added to this paste. These two dispersions were used because they are compatible with the epoxy resin itself dispersed in aqueous phase. Table 3: Composition based on Litex  latex and PU Wording 2 F2.1 F2.2 LITEX NX 1200 at 45% 92.38 0 PU 6800 at 33% 0 84.35 TIMREX KS6L 5.07 5.21 ENSACO 260G 2.55 10.43 Total wet 100.00 100.00 Dry extract 49% 44%

Formulation 3: coating compositions from mixtures of formulation 1 and formulation 2

The formulation 1/formulation 2 wet weight ratio is between 90/10 and 85/15. The coating composition comprising Formulation 1 + Formulation 2 is called Formulation 3 and has a solids content of 37.6%. Table 4: Compositions of formulation 3 Wording 3: F3.1 F3.2 F3.3 F1.1/F2.1 85/15 0 0 F1.2/F2.1 0 85/15 0 F1.2/F2.2 0 0 60/40 Isopropanol 1.5 1.5 1.5

From formulation F3.1, different catalyst ratios were tested Table 5: Variants of formulation 3 (amount of catalyst) Wording 3: F3.4 F3.5 F3.1 F3.6 F3.7 F3.8 F1.3/F2.1 85/15 F1.4/F2.1 85/15 F1.1/F2.1 85/15 0 F1.5/F2.1 0 85/15 F1.6/F2.1 85/15 F1.7/F2.1 85/15 Isopropanol 1.5 1.5 1.5 1.5 1.5 1.5

From formulation F3.1, different ratios of flexibilizing base were tested. Table 6: Variants of formulation 3 (latex ratio) Wording 3: F3.1 F3.9 F1.1/F2.1 85/15 90/10 Isopropanol 1.5 1.5

Formulation 4: Primer coat

Table A: Formulation 4 Wording 4 Wet mass (g) Dry mass PU 6800 at 33% 500.00 165.00 ENSACO 260G 60.00 60.00 TIMREX KS6L 30.00 30.00 Total 590.00 255.00 Dry extract: 45%

II - 2. Results:

Formulation 1 (counterexamples): F1.1 F1.2 Control ( ^∗ ) Test 1: Resistance at 200N (mΩ) 93 74 8.0 Test 2: Winding on mandrel Ø = 3mm - - + ( ^∗ ) Strip without coating

Table 7: Properties of 20µm aluminum coated with formulation 1

It is found that the flexibility of the coating is not satisfactory. In addition, its resistance at 200N is too high. Table 8: Properties of 20µm aluminum coated with formula 3 Wording 3: F3.1 F3.2 F3.3 Control ( ^∗ ) Test 1: Resistance at 200N according to diagram 1 (mΩ) 30 45 31 8.0 Test 2: Winding on mandrel Ø = 3mm + + + + Test 3: Dynamic corrosion 23h, Tamb + + + - ( ^∗ ) Strip without coating

In order to optimize crosslinking, a study on the catalyst/crosslinking agent percentage was carried out using formulation F3.1. Table 9: Properties of 20µm aluminums with different percentages of catalyst in formulation 3 Wording 3: F3.4 F3.5 F3.1 F3.6 F3.7 F3.8 Control ( ^∗ ) Test 1: Resistance at 200N according to diagram 1 (mΩ) 34 39 30 31 27 38 8.0 Test 2: Winding on mandrel Ø = 3mm + + + + + + + Test 3: Dynamic corrosion 23h, Tamb + + + + + + - ( ^∗ ) Strip without coating Wording 3: F3.1 F3.9 Test 1: Resistance at 200N according to diagram 1 (mΩ) 30 29 Test 2: Winding on mandrel Ø = 3mm + + Test 3: Dynamic corrosion 23h, Tamb + + Test 3+: Dynamic corrosion 40h 60°C 0.8V + +

As shown by the results in Tables 8, 9 and 10, the aqueous-based protective conductive layer of formulation 3 makes it possible to reduce the resistance of the collector coated with a protective layer and to protect the metal collector from degradation. related to oxygenation in the presence of aqueous electrolyte.

As stipulated in the specifications, formulas F3.9 and F3.1 passed the 4 characterization tests. Formula F3.1 has been evaluated in dynamic corrosion at 60°C.

- Aqueous electrolyte cell

F3.1 Control ( ^∗ ) Test 5: Cell ESR (mΩ) 37 /////// Cycling at room temperature > 90,000 ≈ 0 Cycling at 60°C 10,000 ≈ 0 ( ^∗ ) Strip without coating and with a layer of active material

Table 11: characterizations of an aqueous electrolyte cell prepared from coating F3.1 - Ion electrolyte cell (first variant):

The cell is tested according to test protocol 5. Table 12: characterizations of an ionic liquid cell prepared from coating F3.1 according to variant 1 F3.1 Vmax (V) 3 Capa discharge (F) 9.6 Energy efficiency (%) 95.4 ESR (mΩ) 61

- Ion electrolyte cell (second variant):

The cell is tested according to test protocol 6. Table 13: characterizations of an ionic liquid cell prepared from coating F3.1 + primer according to variant 2 F3.1 + primer Control ( ^∗ ) Vmax (V) 3 Load / unload capacity (F) 14.7/14.0 Capacitive efficiency (%) 95.4 Energy efficiency (%) 76.6 ESR (mΩ) 48 Cycling at room temperature >2000h 0 ( ^∗∗ ) ( ^∗ ) Strip without coating and with a layer of active material
( ^∗∗ ) Bad adhesion of the material

Claims (14)

1. An electrode (2) for electrical energy storage comprising a metallic current collector (3) and an active material (7), the current collector (3) being coated on at least one portion of one of its faces with at least one protective layer (5) placed between the current collector (3) and the active material (7), the protective layer (5) comprising:

   (A) A polymer matrix comprising:

   (A1) At least one crosslinked epoxy polymer or copolymer,

   (A2) At least one elastomer,

   (B) Conductive fillers,

   characterized in that the protective layer (5) comprises:

   - from 30 to 60% of at least one crosslinked epoxy polymer or copolymer (A1),

   - from 10 to 30% of at least one elastomer (A2),

   - from 30 to 50% of conductive fillers (B),
   the sum of the weights of (A1), (A2) and (B) represents from 95 to 100%,

   by weight of dry matter, relative to the total weight of dry matter of the protective layer (5).
2. The electrode (2) as claimed in claim 1, in which the protective layer (5) is obtained by drying and crosslinking an aqueous composition (G) comprising:

   - precursors of the polymer matrix (A):

   - precursors of crosslinked epoxy polymer(s) or copolymer(s) (A1)

   - at least one elastomer (A2),

   - conductive fillers (B).
3. The electrode (2) as claimed in claim 1 or claim 2, in which the current collector (3) is made of aluminium or copper.
4. The electrode as claimed in any one of the preceding claims, in which (A2) is selected from: the elastomers having a film-forming temperature below 20°C.
5. The electrode (2) as claimed in any one of the preceding claims, in which (A1) is selected from: a crosslinked epoxy polymer, a crosslinked epoxy-alkyd copolymer, a mixture of epoxy polymer and crosslinked alkyd resin.
6. The electrode (2) as claimed in any one of the preceding claims, in which (A2) is selected from butadiene-acrylonitrile (NBR) latices and polyurethane latices.
7. The electrode (2) as claimed in any one of the preceding claims, in which (B) is selected from: mixtures of carbon black and graphite.
8. The electrode (2) as claimed in any one of the preceding claims, in which:

   - the polymer composition (A) represents from 50 to 70%,

   - the conductive fillers (B) represent from 30 to 50%,

   and the sum of the weights of (A) and (B) represents from 95 to 100%,

   by weight of dry matter, relative to the total weight of dry matter of the protective layer (5).
9. The electrode as claimed in any one of the preceding claims, in which the protective layer (5) has a thickness in the range from 5 to 50 µm.
10. An electrode fabrication process (2) comprising:

    1- supplying a metallic current collector (3),

    2- preparing an aqueous composition (G),

    3- depositing the composition (G) on at least one portion of one face of the current collector (3),

    4- a first thermal treatment for drying the composition (G),

    5- a second thermal treatment of the coated current collector (3) at a temperature above the glass transition temperature of the crosslinked epoxy polymer or copolymer (A1), and below the degradation temperature of the crosslinked epoxy polymer or copolymer (A1),

    6- depositing a layer of active material on the coated current collector (3), the process being characterized in that composition (G) comprises:

    - from 30 to 60% of precursors of a crosslinked epoxy matrix (A1),

    - from 10 to 30% of at least one elastomer (A2),

    - from 30 to 50% of conductive fillers (B),

    the sum of the weights of (A1), (A2) and (B) represents from 95 to 100%,

    by weight of dry matter, relative to the total weight of dry matter of the aqueous composition (G).
11. A supercapacitor (1) comprising two electrodes (2), at least one portion of which is immersed in an ionic electrolyte, the two electrodes (2) being separated by an insulating membrane (9), at least one of the two electrodes being as claimed in one of claims 1 to 9.
12. The supercapacitor (1) as claimed in claim 11, in which the electrolyte is an aqueous electrolyte.
13. The supercapacitor (1) as claimed in claim 11 or as claimed in claim 12, in which the electrolyte is an ionic liquid.
14. The supercapacitor (1) as claimed in any one of claims 11 to 13, the two electrodes of which are as claimed in any one of claims 1 to 9.

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